Link Aggregation is widely used to aggregate multiple links between a pair of nodes in order to be able to transmit user data on each of the links participating in a Link Aggregation Group (LAG) (see, e.g., IEEE 802.1AX 2008). Aggregating multiple network connections in this fashion can increase throughput beyond what a single connection can sustain, and/or can be used to provide redundancy in case of a failure of one of the links. The “Distributed Resilient Network Interconnect” (DRNI) project (see IEEE 802.1AXbq/D0.4) specifies extensions to Link Aggregation in order to be able to use link aggregation on a network interface even between more than two nodes.
Among its aims, the 802.1AXbq project aims to provide means for enforcing that the frames (e.g. IP packets) of a given conversation are transmitted by a particular physical link. Furthermore, congruency is aimed to be provided—meaning that the same physical link is used for a particular conversation both in the forward and the backward direction. In addition, load balancing is also aimed to be supported, such that multiple links of a LAG are used for frame transmission, and a single link is used exclusively as an “Active” link for all traffic while a “Standby” link goes unused.
In case of a network interface a conversation can be referred to as a service, as typically a service is handed-off through the interface. The service handed-off on an interface may be a Virtual Local Area Network (VLAN) thus the service identifier may be a VLAN Identifier (VID), such as Service VID (i.e. “S-VID”) (typically identifying services on Network to Network Interfaces (NNIS)) or a Customer VID (i.e. “C-VID”) (typically identifying services on User to Network Interfaces (UNIs)).